Shaft kiln



Jan. 12, 1965 A. M. TVERGAARD ETAL 3,165,304

SHAFT KILN Filed Jan. 14, 1963 3 Sheets-Sheet l INV EN TORS 446: M.TVEAGAAPD, ALBERT H. PACK, y WILL/AM W CAMPBELL 5.4434 1.54 T/ldMATTORNEY A. M. TVERGAARD ETAL 3,165,304

Jan. 12, 1965 SHAFT KILN 3 Sheets-Sheet. 2

Filed Jan. 14, 1963 mammals 54494 LEJT/IJM Jan. 12, 1965 A. M. TVERGAARDETAL 3,165,304

SHAFT KILN 3 Sheets-Sheet 3 Filed Jan. 14, 1963 LA ,L

United States Patent 3,165,304 SFAFT KILN Ange M. Tvergaard, Albert H.Pack, and William W.

Campbell, Ludington, Mich, and Earl Leatharn, Wesford, Pa., assignors toHarhison-Walker Refractories Company, Pittsburgh, Pa, a corporation ofPennsylvania Filed Jan. 14, 1963, Ser. No. 251,415 12 Claims. (Cl.2263-29) This invention relates to the construction of shaft kilns foroperation at very high temperatures. More particularly it relates toimproved shaft kiln construction suitable for dead burning magnesite andthe like.

The art of kiln construction is very old and the litera ture,particularly the patent literature, is replete with suggestedconstructions and methods of operation for kilns. One segment of the artof kiln construction or design relates to what is sometimes termed shaftkiln design. Shaft kilns are usually vertical kilns in which a charge ofmaterial 'to be treated is passed downwardly through the open top of thekiln in counter-current flow to an upwardly moving stream of hot gas.This type Previous shaft. kilns for dead burning dolomite. and magnesitehave consisted of a refractory lined steel shell of the type disclosedin said co-pending application. The refractory lining was supported by ahorizontally disposed annular steel plate which was in turn supported bybeams welded to the steel shell. A stainless steel skirt was weldedabout the aperture through this annular plate and 7 extended downwardlytherefrom to (l) confine the mateof kiln has been employed mostfrequently in the calcining of limestone. In calcining limestone it is.desired to drive off certain natural constituents to obtain a chemicallyreactive product. The chemical equation occurs in the I struct kilns fordead burning magnesite and dolomite because the required dead burningtemperature for these materials is above about 3000 F. Some kilns, fordead burning'magnesite and dolomite, now operate between 4000 and 5000F. The 4000 Filigure is more applicable to dolomite. V g

With the lower calcining temperature for limestone it has been possibleto incorporate various modes of auxiliary flow directing apparatusinteriorly of the kiln. These have included sequential burning stages,one under theother in a common kiln shell, which tended to assure thatall of the charge passing through the kiln was heated to at least thedesired disassociation temperature of cal cium carbonate. Variousinternal baffiing arrangements have been suggested to deflect gas flowand charge move ment to produce intimate admixing interiorly of thekiln. Others have suggested a plurality of juxtaposed ducts interiorlyof a common shell as another means of assuring intimate associationbetween the downwardly moving charge of limestone and the upwardlymoving charge or hot gases. However, the foregoing arrangements arenotsuited for the operation of a kiln above about 3000 F. because thetemperatures involved are beyond the range of the normally usedmaterials of construction. A particularly satisfactory design for therefractory lining of tubular shaft kilns of the type to which thisinvention relates is disclosed in co-pending U.S. patent applicationS.N. 203,659 filed July 19, 1962, now abandoned, owned by a commonassignee. In operating kilns of the type disclosed in said co-pendingapplication it has been found diflicult to cool the product uniformly at0 near the bottom discharge.

rial being discharged from the bottom of the kiln and to (2) protect theadjacent metal structural members from the radiant heat of thedischarging product.

This arrangement was not entirely satisfactory. The downwardly extendingskirt was subject to extensive erosionbecause of contact with the hotdischarging material. Further, the skirt was dificult to inspect forsigns of damage, particularly when the kiln operation fluctuated and theproduct discharged at temperatures above 2000 F. Also, above 2000 F. theskirt deformed due to softening of the metal. Furthermore, the margin ofsafety against catastrophic failure of the kiln bottom due to very widefluctuations in the operation of the kiln was not as great'as desired.In a kiln of this design, where the charge is supported by the dischargetable only, with the table in turn held in place by the skirt, a ruptureor even a large deformation of the skirt allows the charge to run offthe edge of the table thus emptying the kiln into the bottom chamber.The 3000-4500" F. material thus discharged into the bottom half of thekiln can melt or otherwise cause irreparable damage to the bottom coneand the structural members which support the kiln.

Accordingly it is an object of this invention to provide improvedconstruction for high temperature shaft kilns. It is another object ofthe invention to provideimproved shaft kiln construction suitable fordeadburning materials above about 3000 F. It is a further specificobject of the invention to provide improved construction for the lowerend of a vertical shaft kiln suitable for dead burning refractorymaterials above about 3000" F.

Other objects, and further features and advantages of this invention.will become readily apparent to those skilled in the art from a study ofthe following detailed description with reference to the appendeddrawings. In these drawings:

FIG. 1 is a schematic side elevation in partial section of the bottom ofa high temperature shaft kiln embodying the concepts of this invention;a

FIG. 2 is a view taken along the line 2-2 of FIG. 1; and

FIG. 3 is a view taken along the line 33 of FIG. 1.

Before describing the drawings in detail it should be understood theyare but exemplary of construction embodying the concepts of ourinvention, and are given by way of explanation and not by way oflimitation.

In FIG. 1 there is shown the bottom portion of a vertical kilnconstructed according to this invention and which is capable of deadburning refractory material above about 3000 F. The kiln includes anupper inlet 8 and a bottom outlet 10 defined by the concentricrelatively thin tubular outer shell 11 and the internal refractorylining 12. Refractory lining 12 is of substantial thickness and may beon the order of two or three feet as compared to the about /2 inchthickness for the shell 11. A burner 16 having a suitable valve 18 (FIG.2) is positioned at the dead burning zone intermediate the ends of thekiln for obtaining temperatures of at least about 3000 F.

A plurality of curved bottom plates 20 are arranged to form an inwardlyconverging skirt of such dimensions as to contiguously abut and supportthe downwardly converging outer surface of the truncated bottom portion13 of the refractory lining 12. The plates 20 have flanges 21 formedabout their upper peripheries. The flanges time it reaches thecombustion zone of the'kiln.

21 have a plurality of apertures formed therethrough adapted forcooperationwith bolts 122,:and apertures" formed through the shelllll,to support the plates 2%;

The other end 23 of each of the plates 26 is likewise apertured andarranged tohavethe upwardly extending car 24' of the retainer ring 25bolted thereto. The ring 25 is arranged to contiguously abut andsupportthe bottom face 26 of the conical portion of the lining. V

The converging portion 13 of the lining is characterized as a generallydownwardly converging truncated elliptical come 13 having atubularpassageof substantially uniform cross-section passingtherethrough. The crosssectional configurationof the passagethroug'h thetruncated elliptical cone section of the lining is substantially f thesame as the cross-sectional configurationof the passage through therefractory lining immediately thereabove. I

It is preferred that the slopeof the downward con vergence or" the outersurface of the bottom of the lining be on the. order of. about 30relative to the vertical.- However, this angle is variable as long as asmalllip remains at thebottom to. form the surface 26 in order toprovide better support for the;lining. Alternatively,- a

plurality ioflugs. (not shownl'may be driven through plates 2t) into thecone portion 13 to provide extra support; Of course, a retainer ring andlugs may be used. In a preferred embodiment, the outer shell 11 extendsa distance beyond the bottom of the refractory lining and Y thenconverges to form a chamber '27 below'plates 2i having a bottom outlet28.

In .a preferred construction an air'inanifold' 29 is positioned belowthe discharge tabledil. Afdrag bar' dl isv positioned between theretainingring 25 and the upper surfaceof the discharge table 39."Opening through the discharge table area series of aperturesinterconnected with theymanifol'd 29 through a plurality of separatecon' duitsrttl' (see FIG. 3); A bathe 43, beneath eachaperture'fifliprevents briquettes 44 from filling the manifold.

Each of the conduits it? has a suitable valvedzl included therein.Bysuitable manipulation of the valves tithe cross-sectionalconfiguration of airbeingintroduccd into the bottom of the kiln may be,adjusted to oil-set horizontal non-uniformity "in the producttemperatures.

By introducing air "through a manifold arrangement.

such as shown in the drawings, it has been found that the averagetemperature'of briquettes' being discharged g from the bottom of theshaftkiln'can be reduced by as i In addition to better cooling of themuch as 500? F. briquettes, the air is more. uniformly preheated by thecampaign production was increased by about20 percent over constructionwithout the manifold. Also, the prod uctwas more uniform.

With the downwardly converging, cross-s'ectionally refractory lining,there is provided greater protection for In one;

-'converging refractory lining. a

.3. In a kiln of the type described in claiml, separate 7 meanspositioned within each manifold compartment to preventcharge materialfrom entering said compartments,

shell below the conical skirtffitl for even closer inspection of theinterior of the "bOllOl'll of the kiln;

Wehavealso discovered that .less' expansion occurs in the metal parts inthe lower portion of the kiln with our construction; This. is 'Tprobablyl' due to, the additional insulation effect provided by theconverging portion of the lining.

Having thus described the invention in detail and with sufiicientparticularity as to enable those skilled in the art'to practice it whatwe desire to have protectedby' Letters Patent-is ,set forth in thefollowing claims'i 1. In a vertical kiln of the type cap'abl e'ofdead'burm ing refractory material above about 3090? 'F.,.said kilnincluding means defining an "upper inlet and af bottom outlet, meanspositioned at a deadburning zone located intermediate the endsfof thekiln arranged to obtain a temperature of at least about 3000*. Fin saiddead burning'zone, a tubular outer shell having'a relativelyrthickrefractory"lining contiguously positioned there-within to define-avertical passage, means arranged-to continuously pass a gas stream inthrough the bottom outletandthe' passa'gein upwardly movingcountercurrent flow; to a downwardly moving chargeof matcrialto be'deadburned, a dischargetable spaced beneath the kiln outlet,-meanspositioned above theftable and beneath the kiln ,outlet' arranged toassure dischargeof material from said table,

the bottom of said refractory'lining, a substantialldistance 1 below thedead burning. zone of the kiln, beingchare acterized as a.downwardlyconverging truncated cone "having a tubularpassage ofsubstantially uniform cross} section passing therethroug'h, plateQmeans, said'p late meanscarried by the :kiln in positiontolcontiguous'ly abut and supper 'ofthe refractory lining;

't the exteriordownwardly converging surface 2. In a vertical kiln ofthetype Ca tesi n buming refractory material above about 3000" F.,xsaidkiln.

including means defiining .an upper-inlet-and a bottom outlet, meanspositioned at a dead ,burning'zone located intermediate the endsfof thekiin'a'rranged'to obtain a temperature of at least'about 30O0" F. insaid dead burn- .re'fractoryi, lining .contiguously. positioned therewithin to define a verticalpassage, a discharge. table. spaced beneath{the kiln outlet, a plurality bf. apertures fo rmed through, thedischarge table, Imanifold means including a plu rality of separatecompartments, said manifold ,mcans supported-beneath thedischargetablesothat each one of its. compa'rtmentsfopensthroughoneiof the dischargetable apertures, means arrangedto separately deliver air 'to each "ofthe separate, compartments. toltliereby pass 7 air through the aperturesin the; discharge table and through the'kiln passage-in upwardlymovingcountercurrent flow to a downwardly .moving charge .of material tobedead burned, the bottom of said refractory lining,

J a-substantial distance below the deadburning zone of elongated,elliptical configuration for the bottom of the the sheet steel adjacentthe bottom of the kiln. Further- Y Y of metal shell Ill in order todetermine the condition of the' support structure for the refractorylining.

desired, ports .(not shown) may be formedthrough'the the kiln, beingcharacterized. a'sia downwardly converg- .ing truncated cone having atubular passage ofsubstantially uniform cross-sectionpassingtherethrough, means carried by the kiln arranged to'supportsaiddownwardly 4. In a kiln of'the'type described in claim 2, adjust ablemeans. carried by said manifold means 'arrangedto adjust the air flow t0the separate compartments of the a .manifold.

5. In, a vertical kiln of the typecapable ofdead burningreftactoryrnatierial above about 3000" R, saidkiln including meansdefining an upper inlet and -a bottorn out- 1et,"means positionedat adead burning zone located intermediate the ends of the kiln arrangedto'obtain a tern V perature of at least about 30OQ- F. in said deadburning zone, a tubular outer-"shellhavinga relatively thick re.-

fractory lining contiguously positioned there within to define avertical passage, a discharge table spaced beneath the kiln outlet, aplurality of apertures formed through the discharge table, manifoldmeans including a plurality of separate compartments, said manifoldmeans supported beneath the discharge table so that each one of itscompartments opens to the discharge table apertures, means arranged todeliver air to each of the separate compartments to thereby pass astream of air upwardly through the discharge table to the kiln passagein upwardly moving countercurrent flow to a downwardly moving charge ofmaterial to be dead burned, the bottom of said refractory lining, asubstantial distance below the dead burning zone of the kiln, beingcharacterized as a downwardly converging truncated cone having a tubularpassage of substantially uniform cross-section passing therethrough,means carried by the kiln arranged to support said downwardly convergingrefractory lining, said outer metal shell extending a substantialdistance below the discharge table to form an enclosed chamber therebeneath, a charge outlet from said chamer, an outlet conduit openingthrough said chamber at a position above the outlet therefrom wherebyexcess air entering through said manifold means may be vented.

6. In a vertical kiln of the type capable of dead burning refractorymaterial above about 3000 B, said kiln including means defining an upperinlet and a bottom outlet, means positioned at a dead burning zonelocated intermediate the ends of the kiln arranged to obtain atemperature of at least about 3000" F. in said dead burning zone, atubular outer shell having a relatively thick refractory lining cont-iuously positioned there within to define a vertical passage, a dischargetable spaced beneath the kiln outlet, a plurality of apertures formedthrough the discharge table, manifold means including a plurality ofseparate compartments, said manifold means supported beneath thedischarge table so that its compartments open through the dischargetable apertures, means arranged to separately deliver air to each of theseparate compartments to thereby pass air through the apertures in thedischarge table and through the kiln passage in upwardly movingcountercurrent flow to a downwardly moving charge of material to be deadburned, the bottom of said refractory lining, a substantial distancebelow the dead burning zone of the kiln, being characterized as adownwardly converging truncated cone having a tubular passage ofsubstantially uniform crosssection passing therethrough, means carriedby the kiln arranged to support said downwardly converging refractorylining.

7. In a vertical kiln of the type capable of dead burning refractorymaterial above about 3000 F., said kiln including means defining anupper inlet and a bottom outlet, means positioned at a dead burning zonelocated intermediate the ends of the kiln arranged to obtain atemperature of at least about 3000 F. in said dead burning zone, atubular outer shell having a relatively thick refractory liningcontiguously positioned there within to define a vertical passage, adischarge table spaced beneath the kiln outlet, a plurality of aperturesformed through the discharge table, manifold means including a pluralityof separate compartments, said manifold means supported beneath thedischarge table so that each one of its compartments opens through oneof the discharge table apertures, means arranged to separately deliverair to each of the separate compartments to thereby pass air through theapertures in the discharge table and through the kiln passage inupwardly moving countercurrent flow to a downwardly moving charge ofmaterial to be dead burned.

8. In a vertical kiln of the type described in claim 1, said plate meansconsisting of a plurality of metal plates, said plates atiixed at oneend to the interior surface of the outer metal shell in position tocontiguously abut and support the exterior downwardly converging surfaceof the refractory lining.

9. In a vertical kiln of the type described in claim 1, there being asubstantially flat surface about the bottom of the refractory liningforming the outlet, said plate means consisting of a plurality of metalplates, said plates afiixed at one end to the interior surface of theouter metal shell in position to contiguously abut and support theexterior downwardly converging surface of the refractory lining, andretainer ring means carried by the other end of said plates contiguouslyabutting said substantially flat surface about the bottom outlet of saidrefractory lining.

10. In a kiln of the type described in claim 7, separate meanspositioned within with each of the separate compartments to preventcharge material from entering said compartments.

11. In a kiln of the type described in claim 7, adjustable means carriedby said manifold means arranged to separately adjust the air flow to theseparate compartments of the manifold.

12. In a vertical kiln of the type capable of dead burning refractorymaterial above about 3000 F., said kiln including means defining anupper inlet and a bottom outlet, means positioned at a dead burning zonelocated intermediate the ends of the kiln arranged to obtain atemperature of at least about 3000 F. in said dead burning zone, atubular outer shell having a relatively thick refractory liningcontiguously positioned therein to define a vertical passage, adischarge table spaced beneath the kiln outlet, a plurality of aperturesformed through the discharge table, manifold means including a pluralityof separate compartments, said manifold means supported beneath thedischarge table so that at least one of its compartments opens througheach one of the discharge table apertures, means arranged to deliver airto each of the separate compartments to thereby pass a stream of airupwardly through the discharge table to the kiln passage in upwardlymoving countercurrent flow to a downwardly moving charge of material tobe dead burned, shell means forming a chamber positioned about thebottom of said kiln arranged to provide for collection of dead burnedmaterial discharging from said table, means forming an outlet conduitopening from said shell means, and means forming a dead burned materialdischarge outlet opening from said chamber at a position below saidoutlet conduit, said outlet conduit normally open to the atmospherewhereby excess air entering through said manifold means may be vented tothe atmosphere.

References Cited by the Examiner UNITED STATES PATENTS 484,999 10/92Curtis et al 50-160 X 696,420 3/02 Dougherty 2l4l8 704,806 8/02 Iamieson50113 1,586,318 5/26 Mabee 263-29 2,628,829 2/53 Ruiz 263-29 2,938,7825/60 Toulmin 266-25 X 2,951,756 9/60 Cavanagh 26625 X 3,003,756 10/ 61Steffensen 263--29 FOREIGN PATENTS 602,653 12/25 France.

CHARLES SUKALO, Primary Examiner.

JOHN J. CAMBY, Examiner.

7. IN A VERTICAL KILN OF THE TYPE CAPABLE OF DEAD BURNING REFRACTORYMATERIAL ABOVE ABOUT 3000* F., SAID KILN INCLUDING MEANS DEFINING ANUPPER INLET AND A BOTTOM OUTLET, MEANS POSITIONED AT A DEAD BURNING ZONELOCATED INTERMEDIATE THE ENDS OF THE KILN ARRANGED TO OBTAIN ATEMPERATURE OF AT LEAST ABOUT 3000* C. IN SAID DEAD BURNING ZONE, ATUBULAR OUTER SHELL HAVING A RELATIVELY THICK REFRACTORY LININGCONTIGUOUSLY POSITIONED THERE WITHIN TO DEFINE A VERTICAL PASSAGE, ADISCHARGE TABLE SPACED BENEATH THE KILN, OUTLET, A PLURALITY OFAPERTURES FORMED THROUGH THE DISCHARGE TABLE, MANIFOLD MEANS INCLUDING APLURALITY OF SEPARATE COMPARTMENTS, SAID MANIFOLD MEANS SUPPORTEDBENEATH THE DISCHARGE TABLE SO THAT EACH ONE